Potomac River Research Articles

Localized Water Quality Improvement in the Choptank Estuary, a Tributary of Chesapeake Bay

Chesapeake Bay has a long history of nutrient pollution resulting in degraded water quality. However, we report improvements in chlorophyll a in surface waters and dissolved oxygen in bottom waters at one of three estuarine stations in the Choptank tributary of Chesapeake Bay. We updated a previous nutrient budget for the estuary constructed for reference year 1998 using rates of atmospheric deposition, inputs of watershed diffuse sources (primarily agriculture), and discharges of point sources (primarily human waste) for reference year 2017. Parallel trends suggest that improvements in water quality at the one station were likely due to 20% reductions in direct atmospheric deposition on the estuary’s surface and 78–95% reductions in wastewater N and P due to installation of tertiary treatment. The agricultural sector, the dominant source of N and P, appeared to provide little contribution to improved water quality during this period. Although efforts to reduce nutrient losses from agriculture are common throughout the Choptank basin, widespread reductions from agricultural diffuse sources could make large contributions to improved water quality at all stations in the estuary. The response in the Choptank is similar to those observed elsewhere in the USA, Europe, Australia, and New Zealand due to improved wastewater treatment. Similar to our findings, the upper Potomac River of Chesapeake Bay saw improvements driven by reductions in atmospheric deposition. Unfortunately, few studies elsewhere have shown improvements in water quality due to agricultural management. The data presented here indicate that public and industrial investments in reductions of atmospheric emissions and upgrades to wastewater treatment plants have improved estuarine water quality in the Choptank.

Stewards of Memory: The Past, Present, and Future of Historic Preservation at George Washington’s Mount Vernon ed. by Carol Borchert Cadou

Reviewed by: Stewards of Memory: The Past, Present, and Future of Historic Preservation at George Washington’s Mount Vernon ed. by Carol Borchert Cadou Anna Nau Stewards of Memory: The Past, Present, and Future of Historic Preservation at George Washington’s Mount Vernon. Edited by Carol Borchert Cadou, with Luke J. Pecoraro and Thomas A. Reinhart. Charlottesville: University of Virginia Press, 2018. ISBN: 9780813941516 Hardcover: 280 pages Mount Vernon is known to most Americans as the historic home of the first president of the United States. It is also considered the birthplace of the historic preservation movement in the United States. The continuing legacy of the latter forms the central subject of Stewards of Memory. This diverse collection of eight concise, readable essays by respected scholars and preservation professionals uses Mount Vernon as a case study offering a cross-section of current theories and practices in historic site preservation and management. These include cultural landscape research, digital documentation tools, and the challenges of achieving more inclusive historic interpretation. The book grew out of a 2013 symposium celebrating the 160th anniversary of the purchase of Mount Vernon by the Mount Vernon Ladies’ Association (MVLA). As the oldest preservation organization in the United States, the MVLA’s contributions to preservation have been well established. The essays here succeed in presenting a window into the paradigms and practices of current work, as lead editor Carol Borchert Cadou, former Senior Vice-President for Historic Preservation and Collections at Mount Vernon, sets forth in the introduction. But the volume would have benefited from an organization that grouped the essays in such a way as to make those themes more apparent. This shortcoming, however, does not detract from the contribution made by each essay. Together, the essays offer enriching interdisciplinary insight into the challenges, needs, and opportunities facing America’s historic sites and house museums in the twenty-first century. This is facilitated by the contributing authors’ diverse backgrounds that include history, architectural history, historic preservation, architecture, archaeology, and collections management. In the opening essay, “New History in Old Buildings,” Carl R. Lounsbury presents an engaging examination of how historic site research and interpretation has evolved over the last fifty years. The new social history methodologies of the 1960s and 1970s fostered broader definitions of historic and architectural value that moved beyond the early twentieth-century model of commemoration and antiquarianism. Drawing on his own experiences at Colonial Williamsburg and other sites in the southeast, Lounsbury traces how scholars have incorporated advances in archaeology and materials analysis along with more inclusive research and survey practices to reach new understandings of sites like Mount Vernon. This research has in turn revised concepts of early American society. Expanded research methodologies are only one part of the preservationist’s toolbox, as George W. McDaniel demonstrates in his essay on “whole place preservation.” In “Stepping Up and Saving Places,” he examines five cases that illustrate varying degrees of success in the preservation of historic sites and their broader environments, including Mount Vernon and the Ashley River region around Drayton Hall in South Carolina, where McDaniel formerly served as director. He argues that effective preservation demands thoughtful management of change in the landscapes surrounding historic sites through proactive, widespread community support. That support requires strong partnerships and advocacy as well as an understanding of larger economic and social contexts. In his essay entitled “’We Have Done Very Little Investigation There; There Is a Great Deal Yet to Do’,” Luke J. Pecoraro examines another aspect of cultural landscape preservation in a brief summary of past and current “Archaeology of George [End Page 43] Washington’s Mount Vernon.” He presents new efforts to understand and protect the larger cultural landscape of the site—the historic core and the original eight thousand acres—as a means to tell a broader history of its multiple generations of owners, occupants, and uses. This includes a program to document forgotten slave cemeteries using GIS (geographic information system) software to analyze historic maps and visitor accounts as well as continued efforts to protect Mount Vernon’s historic viewshed along the Potomac River. Historians of the American preservation movement may find the essays by Lydia Mattice Brandt and Scott...

Daily Precipitation Generation using a Hidden Markov Model with Correlated Emissions for the Potomac River Basin

AbstractA daily precipitation generator based on a hidden Markov model with Gaussian copulas (HMM‐GC) is constructed using remote sensing data from GPM‐IMERG for the Potomac river basin on the East Coast of the USA. Daily precipitation over the basin from 2001–2018 for the wet season months of July to September is modeled using a 4‐state HMM, and correlated precipitation amounts are generated from a mixture of Gamma distributions using Gaussian copulas for each state. Synthetic data from a model using a mixture of two Gamma distributions for the non‐zero precipitation is shown to replicate the historical data better than a model using a single Gamma distribution.

WITHDRAWN: Optimized Suspect Screening Approach for a Comprehensive Assessment of the Impact of Best Management Practices in Reducing Micropollutants Transport in the Potomac River Watershed

WITHDRAWN: Optimized Suspect Screening Approach for a Comprehensive Assessment of the Impact of Best Management Practices in Reducing Micropollutants Transport in the Potomac River Watershed

L’Enfant’s Washington: the figure of the President in the capital of the Republic

ABSTRACT Pierre L’Enfant’s plan for the permanent seat of government on the banks of the Potomac River was completed in 1791. Evidence of L’Enfant’s intentions is limited and the documentation of the debate surrounding its organisation, surprisingly small. However, an examination of the plan, and its correlation with the existing topography and surrounding landscape yields new evidence related to the structure of the most significant axes of the new city. This paper demonstrates the central role of the figure of the President to the location of key buildings and the orientation of avenues. It examines the creation of the persona of George Washington as part of a republican tradition of heroic virtue and explores the extent to which the adoption of a symbolic structure associated with kingship was reconciled with the republican ideals of the new nation. This work questions received ideas as to the distribution of and location of significant institutions and the sequence of design ideas that informed the 1791 plan. More importantly, it embeds Washington, D.C. in a wider history of urbanism as a key location for the early embodiment of American ceremonial life and an early example of structured civic space.

Correction to: Growth models and growing degree-days: assessment of young-of-year alewife and blueback herring in Potomac River tributaries

Due to an oversight during typesetting, the original version of this article unfortunately contained a mistake.

Growth models and growing degree-days: assessment of young-of-year Alewife and Blueback Herring in Potomac River tributaries

Geography and nursery-specific dynamics guide environmental drivers of growth for young-of-year (YOY; larval and juvenile) Alewife (Alosa pseudoharengus) and Blueback Herring (Alosa aestivalis), two species collectively termed river herring; of these factors, temperature is considered one of the most influential. To better understand future YOY growth relative to climate change, this study was designed to determine the site-specific growth rates of YOY river herring in Potomac River tributaries, and determine if temperature was a driving factor of growth. Daily ages were ascertained from YOY otoliths and used to calculate growth rates using nine growth models. Weighted Akaike information criterion (AICw) determined the best-fit model for both species was the von Bertalanffy growth model. Von Bertalanffy growth parameters differed between species (p < 0.0001), between years for both species (p < 0.0001), and between locations for Blueback Herring (p = 0.0002), emphasizing the need for species-specific assessments. Standard length and cumulative growing degree-days were highly correlated within each year for both species, but significantly different between species and years for each species (Pearson’s r = 0.740–0.913, p < 0.0001). Estimating site-specific growth rates and drivers of growth can help managers determine the potential of Potomac River tributaries as viable nurseries in future climates.

A comprehensive study on spectral analysis and anomaly detection of river water quality dynamics with high time resolution measurements

Systemic analysis of hydrology and water quality fluctuations using a data-intensive approach is an emerging research area and is significant for understanding hydrological processes. However, there is very limited understanding of the high-frequency characteristics of water quality fluctuations in the frequency domain. This study proposes a generic systemic framework to comprehensively analyse river water quality dynamics using a combination of Fourier and wavelet spectral analyses with high temporal resolution measurements. This framework identifies long-term, short-term, periodic, aperiodic, normal baseline and abnormal fluctuations, with particularly focus on detecting transient anomaly events due to their importance for watershed management. This study was conducted on the Potomac River, USA, where seven parameters, water temperature (Temp), pH, dissolved oxygen (DO), conductance (Cond), turbidity (Turb), nitrate plus nitrite (NOx-N) and discharge (Disc), were monitored every 15 min for two years at five sites/sub-catchments. Fast Fourier transform (FFT) revealed that Temp, pH and DO exhibited typical low-frequency periodic fluctuations, such as seasonal and bi-annual fluctuations, as well as interesting high-frequency periodic fluctuations, such as 12-hour and 8-hour fluctuations, which were identified as periodic anomalies. Cond, Turb and NOx-N presented universal temporal scaling phenomena, i.e., 1/f fluctuation, at all sites, as shown by the power spectral density. The scaling exponent β ranged between 1 and 3 and presented the order of βCond > βNOx-N > βTurb. The continuous wavelet transform (CWT) associated with contour-based scalograms successfully identified the time, location, duration and magnitude of transient anomaly events and classified two anomaly patterns: abrupt changes and large swings. The two patterns exhibited clearly different spectral energy distributions, i.e., pseudo-frequencies, on the CWT scales. A preliminary causality analysis found that the frequency of occurrence of turbidity anomaly events (FOATurb) was proportional to the product of the developed land area percentage and FOATemp, and FOANOx-N was proportional to the product of forest land area percentage and FOAdisc. Wavelet coherence analysis showed different hysteresis characteristics of different water quality parameters. In particular, Turb and NOx-N presented significantly different coherent fluctuation behaviours between high-frequency and low-frequency regions. Some findings of this study are still difficult to explain at this stage. High-frequency monitoring combined with spectral analysis provides new insights into the details of water quality dynamics, which can help to develop a new index and framework for the reliability, resilience, and management of watershed water quality vulnerability. These results can also be used to design new algorithms for online anomaly detection.

Hyperpigmented melanistic skin lesions of smallmouth bass Micropterus dolomieu from the Chesapeake Bay watershed.

Hyperpigmented melanistic skin lesions (HPMLs) of smallmouth bass Micropterus dolomieu are observed in the Potomac and Susquehanna rivers, Chesapeake Bay watershed, USA. Routine, nonlethal population surveys were conducted at 8 sites on the mainstem Susquehanna River and 9 on the Juniata River, a tributary of the Susquehanna River, between 2012 and 2018, and the prevalence of HPMLs was documented. A total of 4078 smallmouth bass were collected from the mainstem Susquehanna River and 6478 from the Juniata River. Lesions were primarily seen in bass greater than 200 mm, and prevalence in the Susquehanna River (8%) was higher (p < 0.001) than in the Juniata River (2%). As part of ongoing fish health monitoring projects, smallmouth bass were collected at additional sites, primarily tributaries of the Susquehanna (n = 758) and Potomac (n = 545) rivers between 2013 and 2018. Prevalence in the Susquehanna River (13%) was higher (p < 0.001) than the Potomac (3%). Microscopically, HPMLs were characterized by an increased number of melanocytes in the epidermis or within the dermis and epidermis. RNAseq analyses of normal and melanistic skin identified 3 unique sequences in HPMLs. Two were unidentified and the third was a viral helicase (E1). Transcript abundance in 16 normal skin samples and 16 HPMLs showed upregulation of genes associated with melanogenesis and cell proliferation in HPMLs. The E1 transcript was detected in 12 of the 16 melanistic areas but in no samples from normal skin. Further research will be necessary to identify the putative new virus and determine its role in melanocyte proliferation.

Differential migration in Chesapeake Bay striped bass.

Differential migration—increased migration propensity with increasing individual size—is common in migratory species. Like other forms of partial migration, it provides spatial buffering against regional differences in habitat quality and sources of mortality. We investigated differential migration and its consequences to survival and reproductive patterns in striped bass, a species with well-known plasticity in migration behaviors. A size-stratified sample of Potomac River (Chesapeake Bay) Morone saxatilis striped bass was implanted with acoustic transmitters and their subsequent coastal shelf migrations recorded over a 4-yr period by telemetry receivers throughout the Mid-Atlantic Bight and Southern New England. A generalized linear mixed model predicted that ≥ 50% of both males and females depart the Chesapeake Bay at large sizes >80 cm total length. Egressing striped bass exited through both the Chesapeake Bay mouth and Delaware Bay (via the Chesapeake and Delaware Canal), favoring the former. All large fish migrated to Massachusetts shelf waters and in subsequent years repeatedly returned to regions within Massachusetts and Cape Cod Bays. Within this dominant behavior, minority behaviors included straying, skipped spawning, and residency by large individuals (those expected to migrate). Analysis of the last day of transmission indicated that small resident striped bass experienced nearly 2-fold higher loss rates (70% yr-1) than coastal shelf emigrants (37% yr-1). The study confirmed expectations for a threshold size at emigration and different mortality levels between Chesapeake Bay (resident) and ocean (migratory) population contingents; and supported the central premise of the current assessment and management framework of a two-contingent population: smaller Chesapeake Bay residents and a larger ocean contingent. An improved understanding of differential migration thus affords an opportunity to specify stock assessments according to different population sub-components, and tailor reference points and control rules between regions and fishing stakeholder groups.

Recovery of a Tidal Freshwater Embayment from Eutrophication: a Multidecadal Study

Effective management of eutrophication in tidal ecosystems requires a thorough understanding of the dynamics of their responses to decreases in nutrient loading. We analyze a 34-year dataset on a shallow embayment of the tidal freshwater Potomac River, Gunston Cove, for long-term responses of ambient nutrient levels, light transparency measures, phytoplankton biomass, and coverage of submersed aquatic vegetation (SAV) to decreased nutrient loading. Point source loading of phosphorus, the nutrient most limiting primary production in this system, was greatly curtailed coincident with the study onset (1983/84) exhibiting a sharp decrease of 95% from peak loading levels. However, water column total phosphorus decreased much more slowly and gradually. Phytoplankton chlorophyll a did not show a distinctive decrease until 2000 and SAV responded strongly beginning in 2004. The habitat suitability model for SAV developed by Chesapeake Bay researchers was able to explain the recovery of SAV coverage based on data on light transparency and basin morphometry collected in this study. The study results were consistent with the alternative stable state theory with a sharp transition from a phytoplankton-dominated “turbid water” state to an SAV-dominated “clear water” state in a 2-year period from 2003 to 2005. The system eventually responded to nutrient load reductions, but the nonlinear and incomplete nature of this recovery and the two-decade delay illustrate the complexities of managing these systems.

Fish life history trends indicate increasing flow stochasticity in an unregulated river

AbstractLife history theory provides a framework to understand environmental change based on species traits that capitalize on stable, predictable, or stochastic environmental conditions. We evaluated life history strategies and temporal trends in abundance from 1975 to 2017 for 28 fish species within the Potomac River of eastern North America. Multivariate analysis identified life history strategies defined by small‐bodied species with extended spawning seasons and early maturation (opportunistic strategists), large‐bodied species with delayed maturation and long lifespans (periodic strategists), and intermediate‐sized species exhibiting parental care (equilibrium strategists). Linear mixed models detected temporal trends in abundance for 13 species (46%), of which nine increased and four decreased over time. Increasing species were characterized by opportunistic life history strategies (e.g., banded killifish, Fundulus diaphanous; mosquito fish, Gambusia holbrooki), whereas decreasing species were characterized by periodic or equilibrium strategies (e.g., smallmouth bass, Micropterus dolomieu; river chub, Nocomis micropogon). Recent introductions can account for temporal increases in some cases, but most increasing species are native to the study area. Observed increases in opportunistic native species and decreases in periodic and equilibrium species indicate that environmental conditions have become less stable and less predictable over time, consistent with observed increases in spring peak flows in the study area. Our study indicates the importance of environmental stochasticity for fish community responses to land use and climate change and demonstrates the utility of life history theory in this regard.

Bacterial Community Sequences of Submerged Aquatic Vegetation in the Potomac River.

Here, we report results from PCR and sequencing of bacterial 16S rRNA genes from leaf and root surfaces from nine submerged aquatic vegetation (SAV) samples comprising five species. Samples were from four sites along the Potomac River.

“A Region Which Will at the Same Time Delight and Disgust You”: Landscape Transformation and Changing Environmental Relationships in Civil War Washington, DC

“A Region Which Will at the Same Time Delight and Disgust You”Landscape Transformation and Changing Environmental Relationships in Civil War Washington, DC Nathan A. Marzoli (bio) Dragged away from his home in Tompkins County, New York, by war, Capt. Andrew Jackson Grover found himself frustrated by the nation’s capital. Stationed with his regiment at Fort DeRussy, high above the picturesque Rock Creek Valley, Grover penned an eloquent letter to his hometown newspaper about the striking contrasts he saw in the region’s landscape. On one hand, he was struck by the rural beauty of the area, telling his readers, “The road to the city is one of the most romantic I ever traveled. It leads through nearly three miles of woods, compels us to ford streams several times, and continually delights the eye by a panorama of beauty which shows a new scene at every turn.” The officer found beauty in the seemingly well-placed cedar trees that crowded the ravines, “dignified oaks and chestnuts” that crowned the hills, and the magnolias that “range themselves along the roadside like lines of spectators, promising to drop their flowers upon our heads if we came that way next summer.” Yet on the other hand, he also chastised the local farmers, whom he thought had not properly maintained this landscape. He called Washington a “region which will at the same time delight and disgust you.” Grover concluded that the city was almost “designed to give us a perfect contrast,” because in spite of the great rural beauty, “we see only dilapidated dwellings, prostrate fences, meet seldom with any but ignorant bears, and cannot pass a house without being barked at by dogs.”1 Many contemporaries probably would have agreed with Captain Grover in his assessment of Washington as a rural, frustratingly incomplete city. Pierre L’Enfant had ambitiously planned out the new capital city over a large area extending [End Page 125] from the Potomac River and the Eastern Branch (now the Anacostia River) as far as Rock Creek to the west and Boundary Street (present-day Florida Avenue) to the north.2 Even by 1861, the government buildings surrounding the White House and Capitol were still the only substantial structures in Washington City. But even these were widely spaced and often incomplete, leading some of the sixty thousand inhabitants to refer to it as a “city of magnificent distances.” The landscape of the District beyond Boundary Street and into Maryland and Virginia was mostly rural. If travelers followed one of the many dirt tracks (generously called roads) that led them toward the outskirts of the District and eventually into Maryland, they might alternately pass through “lonely tracts of woodlands” that sometimes almost resembled “uncivilized territory”; scattered small farms, as well as farm fields, orchards, and fences; and the occasional stately plantation, many of which were owned by Virginia’s and Maryland’s most influential families. In an era when other American cities were rapidly urbanizing, Washington stayed closely tied to the rural landscape. In fact, its relationship with nature seemed to have remained mostly static since its founding on the Potomac River over half a century before. This connection would change permanently, however, with the outbreak of Civil War.3 When Virginia seceded from the Union in April 1861, Washington’s antebellum relationship with nature—one that kept the city closely tied to the rural landscape—actually posed a threat. Officials worried that Confederate forces might march on the capital, using the heights across the Potomac River to lob shells in among the government buildings. The lack of developed roads, as well as the large tracts of forests and agricultural lands, would also make it difficult for Federal troops to mount an effective defense of the city. Not only would it be challenging to shuffle troops and supplies around a defense system, but the many woodlots and rugged hills would also prevent mounted artillery from maintaining proper fields of fire. Because many in the Federal government realized the key to defending the nation was the strength of the capital city itself, Union forces would need to alter the area’s landscape—and, therefore, rewrite the city’s existing environmental relationships...

Alkalinity in Tidal Tributaries of the Chesapeake Bay

AbstractDespite the important role of alkalinity in estuarine carbon cycling, the seasonal and decadal variability of alkalinity, particularly within multiple tidal tributaries of the same estuary, is poorly understood. Here we analyze more than 25,000 alkalinity measurements, mostly from the 1980s and 1990s, in the major tidal tributaries of the Chesapeake Bay, a large, coastal‐plain estuary of eastern North America. The long‐term means of alkalinity in tidal‐fresh waters vary by a factor of 6 among seven tidal tributaries, reflecting the alkalinity of nontidal rivers draining to these estuaries. At 25 stations, mostly in the Potomac River Estuary, we find significant long‐term increasing trends that exceed the trends in the nontidal rivers upstream of those stations. Box model calculations in the Potomac River Estuary indicate that the main cause of the estuarine trends is a declining alkalinity sink. The magnitude of this sink is consistent with a simple model of calcification by the invasive bivalve Corbicula fluminea. More generally, in tidal tributaries fed by high‐alkalinity nontidal rivers, alkalinity is consumed, with sinks ranging from 8% to 27% of the upstream input. In contrast, tidal tributaries that are fed by low‐alkalinity nontidal rivers have sources of alkalinity amounting to 34% to 171% of the upstream input. For a single estuarine system, the Chesapeake Bay has diverse alkalinity dynamics and can thus serve as a laboratory for studying the numerous processes influencing alkalinity among the world's estuaries.

Identification of Planktothrix (Cyanobacteria) Blooms and Effects on the Aquatic Macroinvertebrate Community in the Non-Tidal Potomac River, USA

Identification of Planktothrix (Cyanobacteria) Blooms and Effects on the Aquatic Macroinvertebrate Community in the Non-Tidal Potomac River, USA

Evaluating a novel sign\u2019s impact on whether park visitors enter a dangerous river

BackgroundBetween 1972 and 2015, 56 visitors to the two national parks that border the Potomac River Gorge experienced fatal drowning. In 2016, the George Washington Memorial Parkway (GWMP), and the Chesapeake and Ohio National Historical Park (CHOH) partnered with a researcher to see if enhancement of their risk communication strategies could reduce behaviors that contribute to these deaths.MethodsAn experimental sign, which informed visitors that water entry was illegal and could result in a fine exceeding $200 was developed, and displayed on alternating weekend days from July 30 to September 11, 2016. Those signs were displayed at each park’s entrance, on restroom doors, at trailheads, and at both shorelines of the Potomac. At other times the experimental signs were covered, but a standard safety sign was always present. Cameras were used to record water entries.ResultsCameras captured 1441 images. Approximately 2% of the images in CHOH and 1% of the images in GWMP showed a visitor in the water. Our multivariate analysis revealed that air temperature, beach count, and sign condition were significantly associated with water entry. When our experimental sign was displayed, the odds of an image showing someone in the water was reduced by 63%.ConclusionsA sign alerting park visitors to the fact that water entry is illegal, and could potentially result in a considerable fine, was associated with significantly reduced risk-taking. While intuitive, this finding is a reminder to consider whether warnings that focus on non-health consequences might be more salient to at-risk populations.

An integrated data-driven framework for surface water quality anomaly detection and early warning

Abstract The surface water quality anomaly detection for rapid early warning is essential to prevent potential harmful compounds, resulting from river environmental spills or intentional releases, from dispersing in large scale. In this study, an effective data-driven framework for surface water quality anomaly detection is developed to provide early warnings for dealing with river environmental pollution in advance. The developed framework is constructed by an integration of Bayesian autoregressive (BAR) model for water quality variation prediction and Isolation Forest (IF) algorithm for water quality anomaly detection. First, an autoregressive method based on Bayesian inference is used to forecast the tendencies of water quality variations. Second, an IF algorithm is applied to identify the features of water quality anomalies using the prediction residuals obtained in the previous stage. The integration framework is then applied to analyze and detect the surface water quality variations and anomalies in Potomac River of West Virginia, USA, comparing with prediction-based anomaly detection method, classification-based anomaly detection method, and different scenarios. The results demonstrate that the developed integration framework not only could enhance water quality anomaly detection accuracy, but also effectively provide early warning for emergency operations in a quick response.

Daily briefing: Dolphins frolic again in the Potomac River

Daily briefing: Dolphins frolic again in the Potomac River

Chromobacterium phragmitis sp. nov., isolated from estuarine marshes.

Thirteen isolates of Gram-stain-negative, motile, violet-pigmented bacteria were isolated from marshes along tidal portions of the Potomac and James rivers in Maryland and Virginia, USA, respectively. 16S rRNA gene sequences and fatty acid analysis revealed a high degree of relatedness among the isolates, and genomic sequencing of two isolates, IIBBL 112-1T and IIBBL 274-1 (from the Potomac and James rivers, respectively), revealed highly similar genomic sequences, with a blast-based average nucleotide identity (ANIb) of ca. 98.7 %. Phylogenetic analysis of 16S rRNA gene sequences suggested that the species most highly related to IIBBL 112-1T were Chromobacterium amazonense, Chromobacterium subtsugae and Chromobacterium sphagni. However, deletion of a 25-nucleotide sequence that may have been horizontally acquired by both IIBBL 112-1T and C. amazonense resulted in a substantially different analysis; in the latter case, the species nearest IIBBL 112-1T were Chromobacterium violaceum, Chromobacterium vaccinii and Chromobacterium piscinae. Whole-genome alignments between either IIBBL 112-1T or IIBBL 274-1 and the type strains of C. vaccinii or C. violaceum resulted in ANIb values in the range of ca. 87 %, while alignment with C. amazonense CBMAI 310T resulted in an ANIb of ca. 83 %. Collectively, these data demonstrate that IIBBL 112-1T and IIBBL 274-1 represent a new taxon within the genus Chromobacterium. We propose the name Chromobacterium phragmitis sp. nov. for this taxon; the type strain is IIBBL 112-1T (=NRRL B-67132T=JCM 31884T).